Aqueous norfloxacin sonocatalytic degradation with multilayer flower-like ZnO in the presence of peroxydisulfate

• Multilayer flower-like ZnO as sonocatalysts were prepared. • Sonocatalytic activity of sonocatalysts was evaluated by degradation of NF . • Na 2 S 2 O 8 and ZnO exhibited a synergistic effect to NF degradation. • The main active oxidative species for NF degradation were determined. Multilayer ZnO nanoflowers were synthesized through a simple precipitation method and characterized by field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), X-ray photoelectron spectra (XPS) and nitrogen absorption-desorption techniques. The FE-SEM images show the integrated morphology of an individual flower-like ZnO nanostructure, which is made of nano-platelets with uniform thickness (20–30 nm). The average pore size and Brunauer-Emmet-Teller (BET) surface area of the as-synthesized ZnO were 27.25 nm and 13.53 m 2 /g. The sonocatalytic ability of the prepared samples was evaluated through norfloxacin (NF) degradation in an aqueous system using ultrasound (US) irradiation. To improve degradation efficiency, peroxydisulfate (Na 2 S 2 O 8 ) was introduced to develop a US/ZnO/peroxydisulfate system, which exhibited an excellent synergistic effect. The effects of ZnO dosage, Na 2 S 2 O 8 concentration, pH, and initial NF concentration were studied to determine the performances of the US/ZnO/peroxydisulfate process. Corresponding results showed that NF degradation rate increased with the increase of ZnO dosage but decreased with the increase of initial NF concentration. Under the optimal Na 2 S 2 O 8 concentration of 0.1 g L −1 at pH 9, the best degradation efficiency can be achieved. Moreover, based on the scavenging experiment results and literatures, NF degradation through US/ZnO/peroxydisulfate system is majorly induced by OH and SO 4 − radicals.